Control mechanism



March 26, 1935.

K. H. HUBBARD ET AL CONTROL MECHANI SM Filed Jan. 17, 1934 @C' 17 Q 10a 16' 2 it W 293 ar fixf g iard ATTORNEY Patented Mar. 26, 1935 UNITED STATES PATENT OFFICE CONTROL MECHANISM New York Application January 1'1, 1934, Serial No. 707,037

9 Claims.

This invention relates to control systems and more particularly to control mechanism suitable for use in pyrometer systems of the recording or regulating type.

It is the purpose of the present invention to provide such controlling mechanisms having relatively few parts which require close manufacturing tolerances and few parts which are subject to wear to such a degree as to affect an accurate and reliable performance of the system even after a long period of continuous operation. In addition, it is the purpose of this invention to provide mechanism which will respond accurately to deflections of the galvanometer needle or other responsive element even as small as a few thousandths of an inch.

The various features of the invention will appear from the detailed description and claims when taken with the drawing in which Fig. 1 is a diagrammatic showing of a recording pyrometer of the automatic potentiometer type; Fig. 2 is a side elevation of the control mechanism with the galvanometer omitted; and Fig. 3 is a front view thereof substantially on the line 33 of Fig. 2.

Referring especially to Fig. 1, 5 designates a galvanometer having a moving coil 6 and a galvanometer needle 7 actuated thereby. This galvanometer coil is connected in an automatic potentiometer or similar electric network including a thermocouple 8, the usual battery 9 and a voltage divider or slide wire 10 with its cooperating fixed contactor 10a.

The mechanism for operating the slide wire 10 to a new null point, as well as the mechanism for moving a stylus S to make a record on a chart C of the temperature to which the thermocouple 8 is exposed, are best shown in Figs. 2 and 3. This mechanism includes a frame 11 having uprights such as 12 and 13 in which a shaft 14 provided with cams l6 and 17, is journaled. This shaft is continuously driven through bevel gears 14a by a synchronous motor 15 (Fig. 1) which also operates through suitable gearing to drive chart 0 at a predetermined rate. A slidable plate 18 adapted to reciprocate in a vertical direction carries at its lower end a roller 19 which engages the periphery of the cam 16 to move the plate downward. The plate at its upper end, is bifurcated and the ends of the two branches have mounted thereon rollers 20 and 21. These rollers support the plate on the inclined surfaces of the scissors arms 22 and 23 which are rotatably mounted on shaft 46, journaled in the vertical uprights 13 and 13a. Coil springs 25 and 26 attached to the arms 22 and 23 and to stud 39 tend to swing these arms to the position shown against fixed stop 24. Lever 27, pivoted at 28 on the upright 13, is provided at one end with a pin 29 which engages a slot in plate 18 and is provided at its other end with a pin 30 engaging a slot 31 in the lower end of the link 32. The upper end of this link is pivoted at an intermediate point 33 on the curved exploring arm 34 of a bell crank pivoted at 35 on an extension of the frame. It will be understood that the upward movement of the exploring arm is limited by its engagement with galvanometer needle 7. The other arm 36 of this bell crank is provided with a pin 37 to which there is connected a coil spring 38, in turn, attached to the fixed stud 39. The free end of the arm 34 has a pin 40 which engages the slot 41 in the upper end of the link 42. A clamping arm 54 also pivoted at 35 has an angular extension 55. This extension, as shown in Fig. 3, is resiliently held in engagement with the arm 36 by spring 56 surrounding pivot 35, which spring at one end engages the extension 55 and at its other end engages the upper surface of the exploring arm '34. It will be noted that the clamping arm 54 is normally slightly spaced from the free end of galvanometer needle '7, but during operation this am periodically forces the needle upward into engagement with the fixed bar 5'? which is supported on the frame by means not shown.

The link 42 is pivoted at 43 on an extension 44 of an annular disc 45 which is provided with an angular arm 49 projecting between the two scissors arms 22 and 23. Disc 45 is free to rotate on the shaft 46 between the clutch plate 47 which is pinned to the shaft and the clutch plate 48 which is movable axially of the shaft when the clutch is disengaged. The movable plate 48 of the clutch is actuated by a pair of upwardly extending arms 50 of a bell crank pivoted at 52 on the upright 12 which arms are provided at their ends with pins 51 to engage the spaced shoulders on the hub of the clutch plate 48. The other arm 53 of this bell crank carries a roller which is positioned to engage the periphery of the cam 17, while the spiral spring 54' normally tends to force the clutch plate 48 to the right so that the disc 45 will be clamped tightly between clutch plates 4'7 and 48, except when restrained by the bell crank.

On shaft 46 there is secured the slide wire 10 and a driving disc 58, as well as earns 59, 60, 61 and 62 which respectively actuate pairs of contact springs '70, '71, '72 and 73 for purposes to be set forth. The disc 58 drives a tape or belt ,64

about suitable guide rolls 65, 66, 6'7 and 68 (Fig. 1) to move the stylus carried thereby in a horizontal path across the chart C.

In the operation of the system let it be assumed that the change in temperature, to which the thermocouple 8 is exposed, is such that the potentiometer network is unbalanced in a manner so that the coil 6 of the galvanometer swings the needle '7 toward the left. Since the motor 15 is continuously driving the shaft 14 the cam 16 mounted thereon, will periodically force the plate 18 downward from the position in which it is normally supported on the scissors arms 22 and 23, while the cam 1'? acts on bell crank arms 50 and 53 to periodically clutch and declutch disc 45 in timed relation with the movement of plate 18. In the cycle of operation, the cam 17 first declutches the disc 45 so that it tends to rotate counterclockwise, due to the weight of the link 42 pivoted on the disc extension 44, the rotation being limited by the engagement of disc arm 49 with the scissors arm 23. While the disc 45 is still declutched, cam 16 forces plate 18 to its lowest position. As this plate is forced downward the rollers 20 and 21 thereon will ride down the inclined surfaces of the scissors arms, thereby tending to swing and to separate these arms against the tension springs 25 and 26. As the scissors arm 23 opens, it moves away from the arm 49 so that disc 45 continues to rotate counterclockwise until the upper end of the slot 41 on the link 42 engages the pin 40 on the exploring arm 34. Also when this plate moves downward, its slot engages pin 29 to rock the arm 27 about the pivot 28 with the result that the link 32 is permitted to rise. It will be understood that the spring 38 tends to swing the exploring arm 34 upward except when this arm is restrained by link 32. This link, however, is periodically raised when pin 30 on arm 27 is swung upward by the downward motion of plate 18. The upward movement of exploring arm 34, in turn, permits the clamping arm 54 to clamp the galvanometer needle 7 against the fixed bar 57 so that this needle is temporarily held in the position to which it has been advanced by the coil 6. The exploring arm 34, however, continues its upward movement until its upper surface engages the clamped galvanometer needle.

As the exploring arm moves upward, its pin 40 engages the upper end of the slot 41 in link 42 thereby elevating this link causing it to rotate the disc 45 in a clockwise direction to a position corresponding to the new position of the exploring arm which position is such that arm 49 is at the right of its normal position. During the time that the exploring arm is moving upward the cam 17 holds the bell crank arms 50 and 53 in position to disengage clutch plate 48 from disc 45. However, as soon as the plate 18 has reached its lowest position and the exploring arm has been positioned against the galvanometer needle in the manner just described, bell crank 50 by reason of the further rotation of cam 1'] permits clutch plates 47 and 48 to engage disc 45 and the rotation of the cam 16 permits the upward movement of the plate 18. When this plate is elevated the scissors arm 22 engages the angular arm 49 on the disc 45 and as these arms tend to close under the action of springs 25 and 26, arm 22 rotates this disc together with shaft 46 (now clutched thereto) in a counter clockwise direction. As the shaft 46 rotates, it rotates the slide wire 10 with respect to the fixed contactor 10a in a direction tending to restore the potentiometer balance and it also rotates disc 58 thereby driving the tape 64 in a direction to move the stylus S toward the proper point on the chart C so that the change in temperature is recorded thereon. Shaft 46 likewise rotates cams 59, 60, 61 and 62. These cams may have such contours that they close sets of contact springs '70, 71, 72 and 73 to complete various alarm circuits, control circuits and the like, to take care of various operating conditions incidental to the operation of the recording system herein disclosed. It will be appreciated that if there has been a large deviation in temperature, the positioning of the stylus S may be effected in several steps during several upward movements of the plate 18.

On the other hand, let it be assumed that the temperature to which the thermocouple 8 is exposed is such that the galvanometer needle '7 swings to the right, the operation of the system will be identical with that just described except that in this instance when the exploring arm 34 is moved upward into contact with the galvanometer needle it will position the angular arm 49 of the disc 45 at the left of its normal position. Therefore, when the slidable plate 18 permits the scissors arms 22 and 23 to restore to normal, the scissors arm 23 will engage the arm 49 to rotate the disc 45 now clutched to the shaft 46 in a clockwise direction. The rotation of shaft 46 will rotate the disc carrying the tape 64 and the slide wire 10 as well as the cams 59 to 62, inclusive.

We claim:

1. In a system of the class described, means positioned in accordance with a change in a condition to which the system is responsive, a single exploring arm having a curved surface movable into engagement with said means throughout at least a portion of the range of movement thereof, said arm being movable generally at right angles to the plane of movement of said means, a member having a normal position and being adjusted in accordance with the movement of said exploring arm, an element to be moved, means including a periodically actuated clutch for mechanically connecting said element to said menuber, and means for moving/said member to its normal position when thus mechanically connected to said element.

2. In a system of the class described, means including a member actuated in response to a change in a condition to which the system is responsive, means for periodically clamping themember in the position to which it has been moved, a single exploring arm having a curved surface movable into engagement with said member throughout at least a portion of the range of movement thereof, said arm being movable generally in the direction of said clamping means, an element to be adjusted, and means including a clutch for periodically moving said element in accordance with the movement of said exploring arm.

3. In a system of the class described, a movable member actuated in a common plane in accordance with a condition to which said system is responsive, a single exploring arm having a portion of its surface inclined with respect to the plane of movement of said member and being movable about an axis substantially in said plane, means for periodically moving the inclined surface of said arm into engagement with said member throughout the range of movement of said member, an element to be adjusted, and means including a clutch for moving said element periodically in accordance with the movement of said exploring arm.

4. In a system of the class described, means including a galvanometer needle positioned in accordance with a change in a condition to which the system is responsive, a single exploring arm having an unbroken surface movable into engagement with said needle throughout the range of movement thereof, said arm being movable generally at right angles to the plane of movement of said needle, a member having a normal position and being adjusted in accordance with the movement of said exploring arm, an element to be moved, means including a periodically actuated clutch for mechanically connecting said element to said member, and means for moving said member to its normal position when connected to said element.

5. In a system of the class described, means including a galvanometer needle actuated in response to a change in a condition to which the system is responsive, means for periodically clamping the needle in the position to which it has been moved, a single exploring arm having an unbroken surface movable into engagement with said needle throughout the range of movement thereof, said arm being movable generally at right angles to the plane of movement of said needle, an element to be adjusted, and means including a clutch for moving said element in accordance'with the movement of said exploring arm.

6. In a system of the class described, a movable member actuated in a single plane in accordance with a condition to which said system is responsive, a single exploring arm having an unbroken surface, said arm being pivoted approximately in the plane of movement of said member, means for periodically moving the unbroken surface of said arm into engagement with said member throughout the range of movement of said member, an element to be adjusted, and means including a clutch for moving said element periodically in accordance with the movement of said exploring arm.

7. In a system of the class described, means including a galvanometer needle movable clockwise and counter-clockwise generally in a single plane in accordance with a change in a condition to which said system is responsive, a single exploring arm having an unbroken arcuate surface movable into engagement with said needle throughout its possible range of movement, said arm being movable generally at right angles to the plane of movement of said needle, an element to be adjusted, means for periodically moving said exploring arm into engagement with said needle, and means including a clutch periodically operated in timed relation to the periodic movementof said exploring arm for moving said element in accordance with the positioning of said exploring arm.

8. In an arrangement of the class described, an element actuated in response to a change in a condition to be indicated, an exploring arm movable into engagement with said element, a shaft to be adjusted in. accordance with the position of said element, a pair of scissors arms rotatably mounted on said shaft and normally urged to a closed position, a member rotatable on said shaft, said member having a projection positioned between said scissors arms, means for periodically clutching said member to and declutching it from said shaft, means for periodically opening said scissors arms and for moving said exploring arm into engagement with said element in predetermined timed relation to the declutching of said member from saidshaft, means connected with said exploring arm and said member for positioning said member while it is declutched from said shaft, and means for closing said scissors arms during the time that said member is clutched to said shaft whereby said projection with its member clutched to said shaft, is moved to its normal position.

9. In an arrangement of the class described, an element actuated in response to a change in a condition to be indicated, a constantly rotating shaft having two cams of diii'erent contours secured thereto, a second shaft parallel to the first shaft and having a pair of scissors arms rotatably mounted thereon, said arms having their free ends slightly spaced apart, a slidable plate periodically moved downward under the control of one of said cams, said plate being suspended 0 said scissors arms and being pro vided with means effective in the lower positions of said plate for opening said arms, a disc rotatably mounted on said second shaft and having an extension projecting between said scissors arms, means under control of the other of said cams for periodically clutching and declutching said disc with respect to said second shaft, an exploring arm movable under the control of said plate into engagement with said element, means actuated by said exploring arm for positioning said disc during the period that it is declutched from said second shaft, and means operable in response to upward movement of said plate and while said disc is clutched to said second shaft for closing said scissors arms to rotate said extension whereby said second shaft is rotated in accordance with the actuation of said element.

KARL H. HUBBARD. JULES A. WIDHER. 

